Is there any way of knowing if cylinder heads are D port or oval without taking them off . Are there casting numbers that give the info . What about the inlet manifold any numbers on there?
Also to fit a later engine in a Coupe the crossmember cannot be removed to fit a rear sump engine , so you have to fit the front bowl sump to the later engine , does the oil pump and pick up interchange. Believe very early engines had different oil pumps altogether.

Good idea Jim , I know somebody with a USB camera so could have a look .
I had a genuine Cortina Savage with the early engine , made the mistake of fitting a cam and later followers to the engine , no oil pressure and all the oil in the rocker covers.
Did the very early engine ever get fitted to Coupe,s , again any way of knowing visually from outside or by serial numbers.

The part number on the oval port inlet manifold is 702F 9423 AB. It's located behind the carb, read from no.6 cylinder side LH of car. The photo below is from my car, which is definitely an oval port engine.

20180519_175837.jpg (145.18 KiB) Viewed 1555 times

The D port inlet manifold is 722F 9425 AC, again located behind the carb, but facing forward.

Either one will be difficult to read, it's easier to stick the phone in & take a picture, rather than trying to wedge your head in there.

The prefix (first 4 digits) is the bit you are looking for as the differentiator.

Front covers are interchangeable, so a dipstick at the front won't help identification.

Info that I have found , early 66 engines had a small oil pump that was not large enough to supply oil to the main bearings fast enough these engines also had the cam followers with restrictors in them . Fitting later cam followers in early engines gives no oil pressure and rocker covers full of oil.
The next change was to larger oil pump with different mounting stud spacing and the block was different to accommodate this pump . Oil pick up pipe was a push fit into the pump via a O ring but these could often develop a air leak preventing oil pressure build up on a cold engine , cure was to fit a oversize thicker O ring .
Next change was to the rear sump engine , the oil pump was now larger and designed to give a 75psi oil pressure as opposed to 60 psi and now had the oil pick up bolted to the pump. This pump is interchangeable to a earlier engine if fitting a rear sump, but not to the very early 66 style engine .

The early engine runs at 50 against the later engine which runs closer to 75 ( in my experience ) the early engine oil pump is larger than the later one - pic below and the early engine has different tappets.

Trying to determine what engine is fitted in the Coupe , I think we agree that the inlet manifold is D port so hopefully the heads are too. Looking at the block on the drivers side just above the sump line there is a triangular depression on the casting, rubbing my finger over this I can feel a hole so I guess this is the old dipstick guide tube hole . I am hoping this means the engine is a later engine converted to front sump . Question is if it’s a early engine would it not have the depression on the casting as at that time there was no such thing as a rear sump engine , so it must be a later engine converted from rear sump to front sump .